eCall refers to an in-vehicle emergency call service. In the event of a collision involving the vehicle, the eCall In-Vehicle System (IVS) establishes an emergency call via a mobile network to emergency agencies. The IVS can be provisioned for “eCall-only” service or for “mixed-mode eCall” service. In mixed-mode eCall service, the system can be used to perform emergency eCalls as well as non-emergency, subscription-based calls. In eCall-only mode, however, the system can only be activated to make emergency calls, and an IVS in eCall-only mode does not register on the mobile network before the eCall is triggered. Thus, when an eCall emergency is triggered, two operations must be performed: (1) the IVS must first register on an available mobile network, and then (2) the IVS initiates the eCall emergency call. Conventionally, registration of the IVS on the mobile network to place an eCall is performed similar to registration for non-emergency calls.
When the IVS is “roaming” and its Home Public Land Mobile Network (HPLMN) or “home network” is unavailable, the IVS must register on a Visitor Public Land Mobile Networks (VPLMNs) or “roaming network” if one is available. Before a roaming network can register the IVS, however, it must receive permission from the IVS's home network. However, it is not uncommon for such permission to be denied, especially in typical instances where the home network has a roaming registration management policy (RRMP) that only permits registrations (and subsequent call servicing) by preferred VPLMN partners (“preferred partners”) with whom the home network has established favorable business arrangements. Thus, in operation, the home network might automatically reject registrations from non-preferred roaming networks unless and until it receives and accepts a registration request through one of its preferred partners.
Consequently, to make an emergency call while roaming, an eCall-only IVS may have to attempt registering with several available roaming networks before one is finally accepted by the IVS's home network (if at all), and this may take several minutes to succeed (if ever). Thus, conventional roaming registration of the IVS on the mobile network may significantly delay the placing of the emergency call—a call that is critically important to successfully register as quickly as possible.